Metallic coating of metal tubes and similar work pieces

ABSTRACT

A method and means of continuously applying molten coating metal, as in galvanising of tubes or members which must pass through the galvanising bath in a straight line, in which the molten metal is passed through a zone beneath a reservoir for the molten metal from which molten metal is discharged onto the tube or rod and the flow around the tube or rod is controlled by a splash plate, and from which the excess coating material flows back to a kettle or the like from which it was originally pumped to the reservoir.

United States Patent Raymond Apr. 15, 1975 [22] Filed:

[5 METALLIC COATING OF METAL TUBES AND SIMILAR WORK PIECES [76]Inventor: Anthony John Raymond, 20429 Attica Rd., Olympia Fields, 111.60461 Apr. 12, 1973 [21] App], N0.: 350,535

[52] US. Cl. 427/345; 118/405; 118/419; 427/367; 427/420; 427/433 [51]Int. Cl. C23c l/00 [58] Field of Search 117/102 A, 114 A, 94; 118/404,405, 419, 420

[56] References Cited UNITED STATES PATENTS 6/1968 Burch 118/405 2/19683,533,761 Pierson 117/114 A Primary Examiner-Mayer Weinblatt AssistantExaminer-Edith L. Rollins Attorney, Agent, or FirmKinzer, Plyer, Dorn &McEachran [5 7 ABSTRACT A method and means of continuously applyingmolten coating metal, as in galvanising of tubes or members which mustpass through the galvanising bath in a straight line, in which themolten metal is passed through a zone beneath a reservoir for the moltenmetal from which molten metal is discharged onto the tube or rod and theflow around the tube or rod is controlled by a splash plate, and fromwhich the excess coating material flows back to a kettle or the likefrom which it was originally pumped to the reservoir.

10 Claims, 6 Drawing Figures METALLIC COATING OF METAL TUBES AND SIMILARWORK PIECES BACKGROUND OF INVENTION In the art of galvanising steeltubes by the application of molten zinc thereto, one of the problemswhich exists is the surrounding of the tube with the galvanisingmaterial without the tube being bent to pass through a trough or thelike as has been customary when galvanising continuous lengths of wireor strip.

It will be realised that in the galvanising of wires or strips noproblem exists as the wire or strip can be bent by passing it over guiderollers to extend down into the galvanising bath and can then be guidedalong the bath and taken out of the bath at the other end by againpassing around appropriately positioned guide rollers, but when it isnecessary to galvanise tubing or larger rods or members which can not bebent, and which have a length such that they cannot be submerged in thebath, the method used for galvanising is to pass the products through atrough which had closed ends and sides and into which the galvanisingliquid is pumped, the trough having apertures in its end so that thetube can pass into the trough at one end and out at the other with aminimal spill of galvanising through the apertures.

Processes of the type described are used particularly in the continuousformation of tubes which are then galvanised and cut into length, theforming of the tubes being usually effected from flat strip which ispassed through forming guides and bent to tubular form and the joint isthen welded to give a continuous tube, means being used to cutoff anyprojecting metal at the weld. the tube being then usually heated byinduction in an inert atmosphere and is passed into the galvanisingsection in which the trough is positioned above the level of the moltenzinc in the kettle, this section usually also being maintained in aninert atmosphere by enclosing the top of the kettle and the trough. Onleaving the trough excess zinc is removed from the tube by means of anair knife or the like surrounding the tube, the excess zinc flowing backinto the kettle, the tube passing out of this zone to a flying shearwhich then cuts the formed and galvanised tubing to length.

The present invention relates generally to this type of process but isnot necessarily limited thereto as it can be applied anywhere where tubeor conduit or rod or the like, which will generally be referred to as awork piece" requires to be continuously passed through a metal coatingzone while maintaining linear alignment of the work piece being coated.

Certain objections exist to the use of a trough which has ends and sidesand has sealed apertures through which the work piece to be treated mustpass, one of these being to obtain optimum size of the apertures inrelation to the tubing to ensure that especially at the I exit end thecoat of galvanising material which has been to ensure that the levelwill be maintained and also to ensure that there will be a correcttemperature gradient over all parts of the trough for most effectivegalvanis- These and other problems are overcome by the present inventionwhich is preferably applied to the galvanising of tubes or similar workpieces of a rigid nature such that they must be fed through thegalvanising bath without disturbing the linear alignment, but it is tobe clear that the invention need not necessarily be limited to thegalvanising of tubing formed by wrapping and welding strip whicheventually, after galvanising, is cut into lengths.

SUMMARY OF INVENTION The process according to the present inventionconsists of flowing the molten metal (e.g. galvanising material) overthe work piece from a reservoir while using a splash plate to direct theflow around the work piece in the most effective manner.

The splash plate is open ended and can be in the form of a tube, eitheropen at the top or closed but connected to the reservoir to receive themolten galvanising material from slots or apertures in the reservoir.The space between the splash plate and the work piece can be relativelynarrow as the supply of the galvanising fluid is constantly replenishedfrom the reservoir, and because of this the ends of the splash plate canbe open as flow control can be regulated by dimensions of the space andthe length of the splash plate.

According to this invention therefore the hot molten metal which may bezinc, or zinc with an additive such as aluminum. flows from thereservoir where it is maintained at the correct temperature by heatingmeans, and into which it is pumped from thevkettle in regulatedquantities, flows from the bottom of the reservoir over the work pieceas it moves in a straight line beneath the reservoir, but to control theflow around the work piece, the splash plate is used to ensure that thework piece is completely surrounded by the galvanising fluid and alsobecause the splash plate can have relatively small dimensions betweenthe splash plate and the work piece, longitudinal flow can be induced ofthe galvanising medium which can be controlled in its direction byshaping of the splash plate or by inclining the splash plate, so that amuch better form of control of the galvanising can be achieved by thepresent invention.

It will be obvious that the apertures in the reservoir through which theflow takes places on to the work piece, can be variously positioned andcan be of any selected shape from perhaps a long slit in the bottom ofthe reservoir corresponding to the medial line of the tube which isdisposed to move beneath the slit, to a series of apertures along thereservoir to control the amount of galvanising liquid at any particularpart of the work piece as it moves through the splash plate.

Because excess liquid can flow from the ends of the splash plate, whichare not obstructed, and flow can also take place over the walls of thesplash plate if these are relatively low in relation to the top of thework piece, advantages in control will be obvious as opposed to a workpiece simply passing through a bath of the molten galvanising fluid byentering the bath through an aperture in one end and leaving the baththrough an aperture in the other end.

Further details of the invention will be appreciated from a descriptionwhich will be made of preferred forms illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic sectional sideelevation of a tube galvanising plant showing the tube passing throughan area below a reservoir and with a splash plate to regulate the flow,the kettle from which the galvanising fluid is pumped to the reservoirbeing shown below the reservoir so that surplus galvanising fluid passesback to the kettle.

FIG. 2 is a section of the reservoir and tube and splash plate on line2-2 of FIG. 1.

FIG. 3 shows a modified form of the invention utilising a long slit todischarge into a tubular splash plate.

FIG. 4 is a section of the unit shown in FIG. 3 as on line 44 of FIG. 3;

FIG. 5 is a view similar to FIG. 3 but showing a further modified formof the device in which a tiltable splash plate is used to furtherregulate the flow of the galvanising fluid; and

FIG. 6 is a view similar to FIG. 4 showing a modified form of splashplate.

DESCRIPTION OF PREFERRED EMBODIMENT In the embodiment shown in FIG. 1 akettle I has in it the molten galvanising fluid 2 which is pumped by anyconvenient pumping device to the reservoir 3 through the pipe 4.

The reservoir comprises walls 5 at the sides and ends and a bottom 6which has in it a series of apertures 7 through which molten materialpumped into the reservoir flows onto the tube 8 which forms the workpiece in this case, the tube 8 being however surrounded on its undersideand sides by the splash plate 10 which is open at the top so that thefluid from the reservoir can flow onto the tube and is then guidedaround the tube by the splash plate 10.

It will be noted that the splash plate has open ends as fluid controlcan be effected by the size and positioning of the apertures 7 and alsoby the proximity of the splash plate to the tube 8 being treated.

As shown in FIG. 1, the level of molten coating metal should be as closeas practical to the underside of the splash plate to maintain the splashplate hot thereby to prevent chilling and freezing of the molten metalin contact with the splash plate. In this same connection, heatexchangers as the plates 9, extend from the splash plate into the bodyof molten metal in the kettle.

As shown in the illustration. the galvanising fluid 2 flows back intothe kettle 1 through the open ends of the splash plate I0, but dependingon the height of the walls of the splash plate 10, it could also flowover the walls back into the kettle.

A preheating induction coil 11 is shown surrounding the tube 8 as itenters the galvanising area, this being general practice as it isnecessary to raise the tube 8 to a selected temperature to ensurecorrect galvanising.

As the galvanising is preferably carried out in an inert atmosphere, acover 12 is illustrated which encloses the space above the kettle l andincludes the reservoir and complete galvanising area.

Excess galvanising fluid can be removed from the tube 8 by any of theknown means, but in the illustra-' tion an air knife 14 is shown whichremoves the excess galvanising material which returns to the kettle.

tle.

Guides 15 and 16 are shown for the tube 8.

Heater elements 17 surround the reservoir maintain the moltengalvanising fluid at the required temperature.

In the modification shown in FIGS. 3 and 4, the reservoir 20 is againprovided with heating means 21 but in this case has a slit 22 along itsbottom, coinciding with the axis of the tube which passes beneath thereservoir.

The tube is designated 23 and as will be seen particularly from FIG. 4the splash plate 24 is in this case in the form of a tube with directcommunication at its top through the aperture 22 with the reservoir 20so that in this case the molten galvanising fluid flows along the tubeas the tube moves through the splash plate 24 to discharge at the openends of the splash plate 24 and it will be noted that in such a casethere is a flow both in the direction of movement of the tubular workpiece 23 and against the direction of movement of the work piece 23 andby for instance regulating the size of the slit or opening 22 the volumeof flow can be controlled so that instead of the tubular work piecemoving through a reservoir as in the prior art embodiments where itmoves through what is virtually a static supply of molten fluid,galvanising according to this present system is by regulating flow alongthe tubular work piece by discharging onto the work piece and then'guiding flow by means of the splash plate.

In FIG. 5 is shown reservoir 30 again with heating means 31 but in thiscase apertures 32 are shown in the bottom of the reservoir and thesefeed the molten liquid through a slit or opening 34 in the tubularsplash plate 35, but in this case the tubular work piece 36 is notconcentrically disposed within the splash plate as for instance in FIGS.3 and 4 but the splash plate 35 is inclined so that at the entry end ofthe tubular work piece 36 it is lower than at the exit end of the workpiece 36, this then encouraging a greater flow in counter direction tothe movement of the tubular work piece 36 and again giving enhancedcontrol over the galvanising action.

In FIG. 6 is shown a still further modification and in this case thereservoir 40 which again has heating elements 41 within it, is simplyprovided with a longitudinal slit 42 through which the moltengalvanising fluid flows onto the travelling tubular work piece 43, butin this case a pair of splash plates 44 and 45 are shown which serve toguide the molten material around the tube and these splash plates candischarge through an opening 46 between their lower ends, back into theket- Thus it will be seen from the various embodiments just describedthat the mode of practice can be varied quite considerably, but thebasic principle is maintained under which the tubular or other workpiece does not pass through a trough containing the molten coatingmetal, and which under the prior art conditions is required to bemaintained beneath the fluid level therein.

According to the present invention the reservoir merely serves as ameans of supply of molten metal flowing through apertures or slits inthe reservoir downward onto the work piece which passes beneath thereservoir and thus has a flow over the work piece for the purposes ofeffecting galvanising. It will be realised that the splash plate formcan be greatly varied because the purpose of this is to regulate theflow around the tubular work piece. Thus the splash plate or splashplates can obviously take various forms and could be of relatively smalldimensions; also the splash plates need not necessarily be continuousbut could be longitudinally sectioned and be associated with outletsfrom the reservoir, all such modifications falling within the spirit ofthe present invention which resides as stated, in the principle offlowing the molten galvanising fluid from a reservoir onto the workpiece to be galvanised and using a splash plate of any required form, ormultiple splash plates to ensure that the galvanising fluid is correctlyguided in relation to the work pieces as it passes through thegalvanising zone.

I claim:

1. The method of continuously applying a molten metal galvanisingcoating to a metal tube or other work piece which must pass through thecoating metal in a straight line inside a housing, said housing havingan entrance opening and an exit opening equipped with a guide for thework piece, comprising heating the metal in a kettle to provide a bodyof liquid metal, pumping the molten metal into a reservoir locatedwithin the housing and above said kettle, allowing a controlled streamof molten metal to flow from said reservoir, passing the work piecethrough the housing along a path beneath said reservoir to allow themolten metal to flow over said work piece, disposing a splash platebeneath said work piece to control the flow of molten metal around thesaid work piece, allowing free flow of the molten metal outward of theend of the splash plate adjacent the exit opening and positioning theguide at the exit opening forward of the adjacent end of the splashplate so that the work piece will unobstructedly drag molten metal fromthe splash plate during its transit from the splash plate to the exitopening guide.

2. The method of claim 1 wherein said splash plate is an open ended tubeat least partly surrounding the lower part of said work piece, butopening to said reservoir to guide molten metal around said work pieceand back to said kettle, and wherein heat exchange is effected betweenthe splash plate and the molten metal in the kettle.

3. The method of claim 2 wherein said splash plate is tilted in relationto the direction of movement of the work piece to control flow of themolten metal along and around said work piece.

4. The method of claim 1 wherein a splash plate is used on each side ofsaid work piece to guide molten metal around said work piece.

5. The method of claim 4 wherein the arrangement of said splash platesleaves an elongated opening beneath said work piece to allow return ofmolten metal to said kettle through said opening.

6. The method of claim 1 wherein a heat exchange is effected between thereservoir and the body of molten metal in the kettle.

7. The method of claim 6 wherein the reservoir is heated independentlyof the kettle.

8. The method of continuously galvanising steel tubes or other workpieces which must pass through the galvanising bath in a straight lineinside a housing which has an entrance opening and an exit opening forthe work piece, comprising heating the galvanising bath in a kettle toform a molten mass, pumping the molten galvanising medium into areservoir disposed above the said kettle and extending along the line ofmovement of the work piece, heating the molten galvanising medium insaid reservoir to maintain galvanising temperature, allowing acontrolled stream of galvanising medium to flow downward from the saidreservoir through an opening in said reservoir, passing the work piecebeneath the said reservoir to have the galvanising medium flow over thesaid work piece as it passes progressively beneath said reservoir,disposing at-least one splash plate adjacent to said work piece tocontrol the flow of the galvanising medium around and along the saidwork piece and back to said kettle, allowing free flow of the moltenmetal outward of the end of the splash plate which is adjacent the exitopening in the housing, and positioning the guide at the exit openingforward of the adjacent end of the splash plate so that the work piecewill unobstructedly drag molten metal from the splash plate during itstransit from the splash plate toward the exit opening guide.

9. The method of claim 8 wherein a heat exchange is effected between themolten medium in the reservoir and in the kettle.

10. The method of claim 9 wherein the reservoir is heated independentlyof the kettle. t

1. The method of continuously applying a molten metal galvanisingcoating to a metal tube or other work piece which must pass through thecoating metal in a straight line inside a housing, said housing havingan entrance opening and an exit opening equipped with a guide for thework piece, comprising heating the metal in a kettle to provide a bodyof liquid metal, pumping the molten metal into a reservoir locatedwithin the housing and above said kettle, allowing a controlled streamof molten metal to flow from said reservoir, passing the work piecethrough the housing along a path beneath said reservoir to allow themolten metal to flow over said work piece, disposing a splash platebeneath said work piece to control the flow of molten metal around thesaid work piece, allowing free flow of the molten metal outward of theend of the splash plate adjacent the exit opening and positioning theguide at the exit opening forward of the adjacent end of the splashplate so that the work piece will unobstructedly drag molten metal fromthe splash plate during its transit from the splash plate to the exitopening guide.
 2. The method of claim 1 wherein said splash plate is anopen ended tube at least partly surrounding the lower part of said workpiece, but opening to said reservoir to guide molten metal around saidwork piece and back to said kettle, and wherein heat exchange iseffected between the splash plate and the molten metal in the kettle. 3.The method of claim 2 wherein said splash plate is tilted in relation tothe direction of movement of the work piece to control flow of themolten metal along and around said work piece.
 4. The method of claim 1wherein a splash plate is used on each side of said work piece to guidemolten metal around said work piece.
 5. The method of claim 4 whereinthe arrangement of said splash plates leaves an elongated openingbeneath said work piece to allow return of molten metal to said kettlethrough said opening.
 6. The method of claim 1 wherein a heat exchangeis effected between the reservoir and the body of molten metal in thekettle.
 7. The method of claim 6 wherein the reservoir is heatedindependently of the kettle.
 8. The method of continuously galvanisingsteel tubes or other work pieces which must pass through the galvanisingbath in a straight line inside a housing which has an entrance openingand an exit opening for the work piece, comprising heating thegalvanising bath in a kettle to form a molten mass, pumping the moltengalvanising medium into a reservoir disposed above the said kettle andextending along the line of movement of the work piece, heating themolten galvanising medium in said reservoir to maintain galvanisingtemperature, allowing a controlled stream of galvanising medium to flowdownward from the said reservoir through an opening in said reservoir,passing the work piece beneath the said reservoir to have thegalvanising medium flow over the said work piece as it passesprogressively beneath said reservoir, disposing at least one splashplate adjacent to said work piece to control the flow of the galvanisingmedium around and along the said work piece and back to said kettle,allowing free flow of the molten metal outward of the end of the splashplate which is adjacent the exit opening in the housing, and positioningthe guide at the exit opening forward of the adjacent end of the splashplate so that the work piece will unobstructedly drag molten metal fromthe splash plate during its transit from the splash plate toward theexit opening guide.
 9. The method of claim 8 wherein a heat exchange iseffected between the molten medium in the reservoir and in the kettle.10. The method of claim 9 wherein the reservoir is heated independentlyof the kettle.